Tzu-Chung Yenn

A study of control room staffing and workload from the human information processing perspective

This study examines the effectiveness of information presentation and task operation in the main control room (MCR) from the human information processing (HIP) perspective. Their influences on operator workloads and implications to staffing are also discussed. The personnel from the Lungmen Nuclear Power Plant in Taiwan were selected as the target sample. A Total of 75 valid questionnaires were analyzed. The results showed that there were significantly different “perception”, “cognition”, “vocal response”, and “workload” between the shift supervisor (SS), reactor operator (RO), and assistant reactor operator (ARO). These different stages of HIP were positively correlated with each other. The result also showed that the workload of the operator was correlated with how they were involved in the HIP stages. This HIP analysis provides a useful way to further understand why their workload might be different with respect to their staffing roles and responsibilities in a hope to re-organize and redesign their tasks in order to prevent from human errors in the future.

A review of current human reliability assessment methods utilized in high hazard human-system interface design

This paper has three objectives. The first is to discuss the role that human reliability assessment implemented in human systems interface design. The second is to present significant characteristics of available HRA techniques. The third is to provide our viewpoints of the applicability of HRA methods in HIS design. Generally, HRA approaches advocate seven stages, problem definition, performances shaping factors analysis, task analysis, human error analysis, effect analysis, error reduction strategies, and evaluation of recommendations. The most difficult technique is the human error probability estimation and prediction. There are four shortcomings of past human error probability estimation and prediction methods. First, the reliable data is deficient. Second, there are insufficient criteria for choosing PSFs. Third, there is a limited capacity for evaluating cognitive behavior. Finally, possible causes are ignored. To look into the above-described problems, this study reviewed present HRA methods and proposed several aspects for future HRA method development.

A mental workload predicator model for the design of pre alarm systems

This study investigated the operators mental workload of the fourth Nuclear Power Plant in Taiwan. An experiment including the primary and secondary tasks was designed to simulate the reactor shutdown procedure of the Nuclear Power Plant. The performance of secondary task, the subjective mental workload and seven physiological signals of participant were measured. The Group Method of Data Handling (GMDH) was applied to integrate these physiological signals to develop a mental workload predictive model. The relationship between subject mental workload and the performance of secondary task is highly correlated with Pearson correlation coefficient as 0.691. The validity of the proposed model is very high with R2=0.85. The proposed model is expected to provide supervisor a reference value of operators performance by giving physiological signals. Besides nuclear power plant, the proposed model could be applied to other fields such as aviation, air transportation control, driving and radar vigilance, etc.

Apply Performance Evaluation Matrix on Investigating Human Error Events in the Main Control Room

Digitalized nuclear instruments and control systems have become the main stream design for the main control room (MCR) of advanced nuclear power plants (NPPs) nowadays. Digital human-system interface (HSI) could improve human performance and, on the other hand, could reduce operators’ situation awareness as well. It might cause humans making wrong decision during an emergency unintentionally. Besides, digital HSI relies on computers to integrate system information automatically instead of human operation. It has changed the operator’s role from mainly relating operational activity to mainly relating monitoring. However, if operators omit or misjudge the information on the video display units or wide display panel, the error of omission and error of commission may occur. Therefore, how to avoid and prevent human errors has become a very imperative and important issue in the nuclear safety field. This study applies Performance Evaluation Matrix to explore the potential human errors problems of the MCR. The results show that the potential problems which would probably affect to the human performance of the MCR in advanced NPPs are multiple accidents, pressure level, number of operators, and other factors such as working environmental.Copyright

Allocating Human-System Interfaces Functions by Levels of Automation in an Advanced Control Room

Human factors engineering (HFE) focuses on the design of human-system interfaces (HSIs). The HSIs, those NPPs parts that personnel interact with in performing their tasks, included control switches, red, green, amber, and white indictor lights, mimic displays, lighted annunciator panels, and hand-written status boards. The advanced technology has introduced the capability of integrating information from numerous plant systems and supplying needed information to operations personnel in a timely manner. Challenges of the well-integrated computerized control room include ensuring reduced staffing does not treat with increased task complexity, achieving a consistent user interface, ensuring increased automation does not adversely affect the operators mental model of the plant, and systems actually support the operator. This study investigated the process of the HSI functions allocation by considering which functions should be automated and to what extent, which is also called the level of automation (LOA).